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Types of mutagens include | Mutations have many possible causes. Some mutations occur when a mistake is made during DNA replication or transcription. Other mutations occur because of environmental factors. Anything in the environment that causes a mutation is known as a mutagen. Examples of mutagens are shown in Figure 5.21. They include ultravio... | There are three types of radioactive decay: alpha, beta, and gamma decay. In all three types, nuclei emit radiation, but the nature of that radiation differs from one type of decay to another. You can watch a video about the three types at this URL: (17:02). MEDIA Click image to the left or use the URL below. URL: | There are several types of radioactive decay, including alpha, beta, and gamma decay. In all three types, nuclei emit radiation, but the nature of the radiation differs. The Table 1.1 shows the radiation emitted in each type of decay. Type Alpha decay Beta decay Gamma decay Radiation Emitted alpha particle (2 protons a... | There are several types of pathogens that cause diseases in human beings. They include bacteria, viruses, fungi, and protozoa. The different types are described in Table 21.1. The table also lists several diseases caused by each type of pathogen. Many infectious diseases caused by these pathogens can be cured with medi... | There are three types of mechanical waves. They differ in how they travel through a medium. The three types are transverse, longitudinal, and surface waves. All three types are described in detail below. | Most cancers are caused by mutations. Mutations are random errors in genes. Mutations that lead to cancer usually occur in genes that control the cell cycle. Because of the mutations, abnormal cells are allowed to divide. Some mutations that lead to cancer may be inherited. However, most of the mutations are caused by ... |
lakes are not like the ocean because they are made of fresh water and they do not have tides or currents. | Lakes are larger bodies of water. Lakes are usually fresh water, although the Great Salt Lake in Utah is just one exception. Water usually drains out of a lake through a river or a stream and all lakes lose water to evaporation. Lakes form in a variety of different ways: in depressions carved by glaciers, in calderas (... | After a heavy rain, you may find puddles of water standing in low spots. The same principle explains why water collects in ponds and lakes. Water travels downhill, so a depression in the ground fills with standing water. A pond is a small body of standing water. A lake is a large body of standing water. Most lakes have... | Ponds are small bodies of fresh water that usually have no outlet; ponds are often are fed by underground springs. Like lakes, ponds are bordered by hills or low rises so the water is blocked from flowing directly downhill. | Freshwater biomes are defined by their low salt concentration, usually less than 1%. Plants and animals in freshwater regions are adjusted to the low salt content and would not be able to survive in areas of high salt concentration, such as the ocean. There are different types of freshwater biomes: ponds and lakes ( Fi... | Coastal areas have a milder climate than inland areas. They are warmer in the winter and cooler in the summer. Thats because land near an ocean is influenced by the temperature of the oceans. The temperature of ocean water is moderate and stable. Why? There are two major reasons: 1. Water is much slower to warm up and ... | The depression that allows water to collect to form a lake may come about in a variety of ways. The Great Lakes, for example, are glacial lakes. A glacial lake forms when a glacier scrapes a large hole in the ground. When the glacier melts, the water fills the hole and forms a lake. Over time, water enters the lake fro... |
Which type of tissue gives bones their strength? | Bones are organs. Like other organs, they are made up of more than one kind of tissue. There are four different kinds of tissues in bones, as shown in Figure 16.11. From the outside of the bone to the center, the tissues are periosteum, compact bone, spongy bone, and bone marrow. Periosteum is a tough, fibrous membrane... | You can help keep your bones and skeletal system healthy by eating well and getting enough exercise. Weight- bearing exercises help keep bones strong. Weight-bearing exercises and activities work against gravity. Such activities include basketball, tennis, gymnastics, karate, running, and walking. When the body is exer... | Bones are the main organs of the skeletal system. In adults, the skeleton consists of a whopping 206 bones, many of them in the hands and feet. You can see many of the bones of the human skeleton in Figure 16.10. The skeletal system also includes cartilage and ligaments. Cartilage is a tough, flexible connective tissue... | Some people think bones are like chalk: dead, dry, and brittle. In reality, bones are very much alive. They consist of living tissues and are supplied with blood and nerves. | Along with the skin, the integumentary system includes the nails and hair. Both the nails and hair contain the tough protein, keratin. The keratin forms fibers, which makes your nails and hair tough and strong. Keratin is similar in toughness to chitin, the carbohydrate found in the exoskeleton of arthropods. | Specialized cells are organized into tissues. A tissue is a group of specialized cells of the same kind that perform the same function. There are four basic types of human tissues: connective, epithelial, muscle, and nervous tissues. The four types are shown in Figure 16.2. Connective tissue consists of cells that form... |
a supervolcano can change life on earth by | A supervolcano could change life on Earth as we know it. Ash could block sunlight so much that photosynthesis would be reduced and global temperatures would plummet. Volcanic eruptions could have contributed to some of the mass extinctions in our planets history. No one knows when the next super eruption will be. Inter... | The Green Revolution has brought enormous impacts to the planet. | Supervolcano eruptions are extremely rare in Earths history. Its a good thing because they are unimaginably large. A supervolcano must erupt more than 1,000 cubic km (240 cubic miles) of material, compared with 1.2 km3 for Mount St. Helens or 25 km3 for Mount Pinatubo, a large eruption in the Philippines in 1991. Not s... | The exact cause of supervolcano eruptions is still debated. However, scientists think that a very large magma chamber erupts entirely in one catastrophic explosion. This creates a huge hole or caldera into which the surface collapses (Figure 1.1). The caldera at Santorini in Greece is so large that it can only be seen ... | Plate tectonic movements can alter climate. Over millions of years as seas open and close, ocean currents may distribute heat differently. For example, when all the continents are joined into one supercontinent (such as Pangaea), nearly all locations experience a continental climate. When the continents separate, heat ... | The geologic time scale may include illustrations of how life on Earth has changed. Major events on Earth may also be shown. These include the formation of the major mountains or the extinction of the dinosaurs. Figure 11.14 is a different kind of the geologic time scale. It shows how Earths environment and life forms ... |
if you stroke an iron nail with a bar magnet, the nail will become a temporary magnet. | Materials that have been magnetized may become temporary or permanent magnets. An example of each type of magnet is described below. Both are demonstrated in Figure 24.7. If you bring a bar magnet close to pile of paper clips, the paper clips will become temporarily magnetized, as all their magnetic domains align. As a... | A magnet is an object that attracts certain materials such as iron. Youre probably familiar with common bar magnets, like the one in Figure 24.2. Like all magnets, this bar magnet has north and south poles and attracts objects such as paper clips that contain iron. | A magnet is an object that attracts certain materials such as iron. Youre probably familiar with common bar magnets, like the one shown in the Figure 1.1. Like all magnets, this bar magnet has north and south magnetic poles. The red end of the magnet is the north pole and the blue end is the south pole. The poles are r... | Like the electric field that surrounds a charged particle, a magnetic field surrounds a magnet. This is the area around the magnet where it exerts magnetic force. Figure 24.3 shows the magnetic field surrounding a bar magnet. Tiny bits of iron, called iron filings, were placed under a sheet of glass. When the magnet wa... | Magnetism is the ability of a material to be attracted by a magnet and to act as a magnet. Magnetism is due to the movement of electrons within atoms of matter. When electrons spin around the nucleus of an atom, it causes the atom to become a tiny magnet, with north and south poles and a magnetic field. In most materia... | A familiar example may help you understand the vibrating electric and magnetic fields that make up electromagnetic waves. Consider a bar magnet, like the one in the Figure 1.1. The magnet exerts magnetic force over an area all around it. This area is called a magnetic field. The field lines in the diagram represent the... |
Neap tides occur when the sun and moon are | The Suns gravity also pulls on Earth and its oceans. Even though the Sun is much larger than the Moon, the pull of the Suns gravity is much less because the Sun is much farther away. The Suns gravity strengthens or weakens the Moons influence on tides. Figure 14.14 shows the position of the Moon relative to the Sun at ... | Figure 14.13 shows why tides occur. The main cause of tides is the pull of the Moons gravity on Earth. The pull is greatest on whatever is closest to the Moon. Although the gravity pulls the land, only the water can move. As a result: Water on the side of Earth facing the Moon is pulled hardest by the Moons gravity. Th... | At the following URL, read about gravity and tides. Watch the animation and look closely at the diagrams. Then answer the questions below. 1. 2. 3. 4. 5. What causes tides? Which has a greater influence on tides, the moon or the sun? Why? Why is there a tidal bulge of water on the opposite side of Earth from the moon? ... | Tides are daily changes in the level of ocean water. They occur all around the globe. High tides occur when the water reaches its highest level in a day. Low tides occur when the water reaches its lowest level in a day. Tides keep cycling from high to low and back again. In most places the water level rises and falls t... | A common misconception is that the Sun is closer to Earth in the summer and farther away from it during the winter. Instead, the seasons are caused by the 23.5o tilt of Earths axis of rotation relative to its plane of orbit around the Sun (Figure 1.1). Solstice refers to the position of the Sun when it is closest to on... | When a new moon passes directly between the Earth and the Sun, it causes a solar eclipse (Figure 24.20). The Moon casts a shadow on the Earth and blocks our view of the Sun. This happens only all three are lined up and in the same plane. This plane is called the ecliptic. The ecliptic is the plane of Earths orbit aroun... |
if a miner is standing on a fault, the __________ wall is where his safety helmet would be and the __________ wall is where his steel toed boots would be. | There are two types of dip-slip faults. In a normal fault, the hanging wall drops down relative to the footwall. In a reverse fault, the footwall drops down relative to the hanging wall. This diagram illustrates the two types of dip-slip faults: normal faults and reverse faults. Imagine miners extracting a re- source a... | With enough stress, a rock will fracture, or break. The fracture is called a joint if the rock breaks but doesnt move, as shown in Figure 7.10. If the rocks on one or both sides of a fracture move, the fracture is called a fault (Figure 7.11). Faults can occur alone or in clusters, creating a fault zone. Earthquakes ha... | If the blocks of rock on one or both sides of a fracture move, the fracture is called a fault (Figure 1.2). Stresses along faults cause rocks to break and move suddenly. The energy released is an earthquake. How do you know theres a fault in this rock? Try to line up the same type of rock on either side of the lines th... | A rock under enough stress will fracture. There may or may not be movement along the fracture. | A strike-slip fault is a dip-slip fault where the dip of the fault plane is vertical. Strike-slip faults result from shear stresses. If you stand with one foot on each side of a strike-slip fault, one side will be moving toward you while the other side moves away from you. If your right foot moves toward you, the fault... | A strike-slip fault is a dip-slip fault in which the dip of the fault plane is vertical. Strike-slip faults result from shear stresses. Imagine placing one foot on either side of a strike-slip fault. One block moves toward you. If that block moves toward your right foot, the fault is a right-lateral strike-slip fault; ... |
what type of feeder is a sea urchin? | Feeding strategies vary greatly among the different groups of echinoderms. Theres no one food or technique thats shared by all echinoderms. Different eating-methods include: 1. Passive filter-feeders, which are organisms that absorb suspended nutrients from passing water. Some echino- derms use their long arms to captu... | Annelids live in a diversity of freshwater, salt-water, and terrestrial habitats. They vary in what they eat and how they get their food. Some annelids, such as earthworms, eat soil and extract organic material from it. Annelids called leeches are either predators or parasites. Some leeches capture and eat other invert... | Figure 14.29 shows a marine food chain. Phytoplankton form the base of the food chain. Phytoplankton are the most important primary producers in the ocean. They use sunlight and nutrients to make food by photosynthesis. Small zooplankton consume phytoplankton. Larger organisms eat the small zooplankton. Larger predator... | When you think of worms, you probably picture earthworms. There are actually many types of worms, including flatworms, roundworms, and segmented worms. Earthworms are segmented worms. Segmented worms are in the phylum Annelida, which has over 22,000 known species. These worms are known as the segmented worms because th... | The open ocean is a vast area. Food either washes down from the land or is created by photosynthesizing plankton. Zooplankton and larger animals feed on the phytoplankton and on each other. Larger animals such as whales and giant groupers may live their entire lives in the open water. How do fish survive in the deepest... | The echinoderms can be divided into two major groups: 1. Eleutherozoa are the echinoderms that can move. This group includes the starfish and most other echinoderms. 2. Pelmatozoa are the immobile echinoderms. This group includes crinoids, such as the feather stars. Listed below are the four main classes of echinoderms... |
a neutron has about the same diameter as a proton. | Unlike protons and electrons, which are electrically charged, neutrons have no charge. In other words, they are electrically neutral. Thats why the neutrons in the diagram above are labeled n0 . The zero stands for zero charge. The mass of a neutron is slightly greater than the mass of a proton, which is 1 atomic mass ... | A neutron is a particle inside the nucleus of an atom. It has no electric charge. Atoms of an element often have the same number of neutrons as protons. For example, most carbon atoms have six neutrons as well as six protons. This is also shown in Figure below . | A neutron is a particle in the nucleus of an atom that has no electric charge. Atoms of an element often have the same number of neutrons as protons. For example, most carbon atoms have six neutrons as well as six protons. This is also shown in Figure 5.2. | A neutron is one of three main particles that make up the atom. The other two particles are the proton and electron. Atoms of all elementsexcept for most atoms of hydrogenhave neutrons in their nucleus. The nucleus is the small, dense region at the center of an atom where protons are also found. Atoms generally have ab... | The nucleus of the atom is extremely small. Its radius is only about 1/100,000 of the total radius of the atom. If an atom were the size of a football stadium, the nucleus would be about the size of a pea! Click image to the left or use the URL below. URL: Electrons have virtually no mass, but protons and neutrons hav... | All atoms of the same element have the same number of protons, but some may have different numbers of neutrons. For example, all carbon atoms have six protons, and most have six neutrons as well. But some carbon atoms have seven or eight neutrons instead of the usual six. Atoms of the same element that differ in their ... |
which of the following are functions of smooth muscle? | Smooth muscles and cardiac muscles are not attached to bone. Recall that these types of muscles are under involuntary control. Smooth muscle is responsible for the contractility of hollow organs, such as blood vessels, the gastrointestinal tract, the bladder, or the uterus. Like skeletal muscles, smooth muscle fibers d... | There are three different types of muscle tissue in the human body: cardiac, smooth, and skeletal muscle tissues. All three types consist mainly of muscle fibers, but the fibers have different arrangements. You can see how each type of muscle tissue looks in Figure 16.17. Cardiac muscle is found only in the walls of th... | The muscular system consists of all the muscles in the body. This is the body system that allows us to move. You also depend on many muscles to keep you alive. Your heart, which is mostly muscle, pumps blood around your body. Each muscle in the body is made up of cells called muscle fibers. Muscle fibers are long, thin... | When skeletal muscles contract, bones move. But how do muscles make your bones move? A voluntary muscles usually works across a joint. It is attached to both the bones on either side of the joint by strong cords called tendons. A tendon is a tough band of connective tissue that connects a muscle to a bone. Tendons are ... | Your skeletal system gives shape and form to your body, but it also plays other important roles. The main functions of the skeletal system include: The skeletal system is made up of bones, cartilage, and ligaments. The skeletal system has many important functions in your body. What bones protect the heart and lungs? Wh... | Muscles are the main organs of the muscular system. Muscles are composed primarily of cells called muscle fibers. A muscle fiber is a very long, thin cell, as you can see in Figure 16.16. It contains multiple nuclei and many mitochondria, which produce ATP for energy. It also contains many organelles called myofibrils.... |
Which structures are found in the outer ear? | The outer ear includes the pinna, ear canal, and eardrum. The pinna is the only part of the ear that extends outward from the head. Its position and shape make it good at catching sound waves and funneling them into the ear canal. The ear canal is a tube that carries sound waves into the ear. The sound waves travel thr... | The middle ear contains three tiny bones (ossicles) called the hammer, anvil, and stirrup. If you look at these bones in Figure 20.7, you might notice that they resemble the objects for which they are named. The three bones transmit vibrations from the eardrum to the inner ear. They also amplify the vibrations. The arr... | Sound is a form of energy that travels in waves through matter. The ability to sense sound energy and perceive sound is called hearing. The organ that we use to sense sound energy is the ear. Almost all the structures in the ear are needed for this purpose. Together, they gather sound waves, amplify the waves, and chan... | The stirrup in the middle ear passes the amplified sound waves to the inner ear through the oval window. When the oval window vibrates, it causes the cochlea to vibrate as well. The cochlea is a shell-like structure that is full of fluid and lined with nerve cells called hair cells. Each hair cell has many tiny hairs, ... | The stirrup passes the amplified sound waves to the inner ear through the oval window (see Figure 20.7). When the oval window vibrates, it causes the cochlea to vibrate as well. The cochlea is a shell-like structure that is full of fluid and lined with nerve cells called hair cells. Each hair cell has tiny hair-like pr... | Hearing is the ability to sense sound. Sound travels through the air in waves, much like the waves you see in the water pictured below ( Figure 1.1). Sound waves in air cause vibrations inside the ears. The ears sense the vibrations. The human ear is pictured below ( Figure 1.2). As you read about it, trace the path of... |
If a wave strikes a barrier at a 45 angle, what is the angle of reflection? | An echo is an example of wave reflection. Reflection occurs when waves bounce back from a barrier they cannot pass through. Reflection can happen with any type of waves, not just sound waves. For example, Figure 19.15 shows the reflection of ocean waves off a rocky coast. Light waves can also be reflected. In fact, tha... | Refraction is another way that waves interact with matter. Refraction occurs when waves bend as they enter a new medium at an angle. You can see an example of refraction in Figure 19.17. Light bends when it passes from air to water. The bending of the light causes the pencil to appear broken. Why do waves bend as they ... | When a wave is reflected straight back from an obstacle, the reflected wave interferes with the original wave and creates a standing wave. This is a wave that appears to be standing still. A standing wave occurs because of a combination of constructive and destructive interference between a wave and its reflected wave.... | Did you ever notice that when youre walking down a street, you can hear sounds around the corners of buildings? Figure 19.18 shows why this happens. As you can see from the figure, sound waves spread out and travel around obstacles. This is called diffraction. It also occurs when waves pass through an opening in an obs... | If a surface is extremely smooth, as it is in a mirror, then the image formed by reflection is sharp and clear. This is called regular reflection (also called specular reflection). However, if the surface is even slightly rough or bumpy, an image may not form, or if there is an image, it is blurry or fuzzy. This is cal... | Waves interact with matter in several ways. The interactions occur when waves pass from one medium to another. Besides bouncing back like an echo, waves may bend or spread out when they strike a new medium. These three ways that waves may interact with matter are called reflection, refraction, and diffraction. Each typ... |
What percent of chimpanzee DNA is the same as human DNA? | Scientists can compare the DNA or proteins of different species. If the molecules are similar, this shows that the species are related. The more similar the molecules are, the closer the relationship is likely to be. When molecules are used in this way, they are called molecular clocks. This method assumes that random ... | Humans evolved from primates, and apes and humans have a primate common ancestor. About 7 million years ago, chimpanzees (our closest living relatives) and humans shared their last common ancestor. | A persons genome is all of his or her genetic information. In other words, the human genome is all the information that makes us human. And unless you have an identical twin, your genome is unique. No one else has a genome just like yours, though all our genomes are similar. The Human Genome Project ( Figure 1.1) was a... | The bases in DNA do not pair randomly. When Erwin Chargaff looked closely at the bases in DNA, he noticed that the percentage of adenine (A) in the DNA always equaled the percentage of thymine (T), and the percentage of guanine (G) always equaled the percentage of cytosine (C). Watson and Cricks model explained this re... | The various sequences of the four nucleotide bases make up the genetic code of your cells. It may seem strange that there are only four letters in the alphabet of DNA. But since your chromosomes contain millions of nucleotides, there are many, many different combinations possible with those four letters. But how do all... | Animals of the genus Ardipithecus, living roughly 4 to 6 million years ago, had brains roughly the size of a female chimp. Although they lived in trees, they were bipedal. Standing on two feet allows an organism to see and also to use its hands and arms for hunting. By the time of Australopithecus afarensis, between 3.... |
fossiltologists are scientists who study fossils to learn about life in the past. | Fossils are the preserved remains of animals, plants, and other organisms from the distant past. Examples of fossils include bones, teeth, and impressions. By studying fossils, evidence for evolution is revealed. Paleontologists are scientists who study fossils to learn about life in the past. Fossils allow these scien... | Fossils are our best form of evidence about Earth history, including the history of life. Along with other geological evidence from rocks and structures, fossils even give us clues about past climates, the motions of plates, and other major geological events. Since the present is the key to the past, what we know about... | Fossils are our best form of evidence about Earth history, including the history of life. Along with other geological evidence from rocks and structures, fossils even give us clues about past climates, the motions of plates, and other major geological events. Since the present is the key to the past, what we know about... | Of all the organisms that ever lived, only a tiny number became fossils. Still, scientists learn a lot from fossils. Fossils are our best clues about the history of life on Earth. | Geology is the study of the solid Earth. Geologists study how rocks and minerals form. The way mountains rise up is part of geology. The way mountains erode away is another part. Geologists also study fossils and Earths history. There are many other branches of geology. There is so much to know about our home planet th... | That life on Earth has changed over time is well illustrated by the fossil record. Fossils in relatively young rocks resemble animals and plants that are living today. In general, fossils in older rocks are less similar to modern organisms. We would know very little about the organisms that came before us if there were... |
The only cure for kidney failure is a kidney transplant. | You need only one kidney to live a normal, healthy life. A single kidney can do all the work of filtering the blood and maintaining homeostasis. However, at least one kidney must function properly to maintain life. Diseases that threaten the health and functioning of the kidneys include kidney stones, infections, and d... | The kidneys ( Figure 1.1) are important organs in maintaining homeostasis, the ability of the body to maintain a stable internal environment despite a changing environment. Kidneys perform a number of homeostatic functions. They maintain the volume of body fluids. They maintain the balance of salt ions in body fluids. ... | In some cases, certain mineral wastes can form kidney stones ( Figure 1.1). Stones form in the kidneys and may be found anywhere in the urinary system. Often, stones form when the urine becomes concentrated, allowing minerals to crystallize and stick together. They can vary in size, from small stones that can flow thro... | Blood with wastes enters each kidney through an artery, which branches into many capillaries. After passing through capillaries and being filtered, the clean blood leaves the kidney through a vein. The part of each nephron called the glomerulus is where blood in the capillaries is filtered. Excess water and wastes are ... | HIV, or human immunodeficiency virus, causes AIDS. AIDS stands for "acquired immune deficiency syndrome." It is a condition that causes death and does not have a known cure. AIDS usually develops 10 to 15 years after a person is first infected with HIV. The development of AIDS can be delayed with proper medicines. The ... | The kidneys help the body maintain homeostasis in several ways. They filter all the blood in the body many times each day and produce urine. They control the amount of water and dissolved substances in the blood by excreting more or less of them in urine. The kidneys also secrete hormones that help maintain homeostasis... |
_Relative dating can be used to determine how long ago a fossil organism lived. | Fossils are useful for reconstructing the past only if they can be dated. Scientists need to determine when the organisms lived who left behind the fossils. Fossils can be dated in two different ways: absolute dating and relative dating. Absolute dating determines about how long ago a fossil organism lived. This gives ... | An index fossil can be used to identify a specific period of time. Organisms that make good index fossils are distinctive, widespread, and lived briefly. Their presence in a rock layer can be used to identify rocks that were deposited at that period of time over a large area. | Fossils are used to determine the ages of rock layers. Index fossils are the most useful for this. Index fossils are of organisms that lived over a wide area. They lived for a fairly short period of time. An index fossil allows a scientist to determine the age of the rock it is in. Trilobite fossils, as shown in Figure... | An index fossil can be used to identify a specific period of time. Organisms that make good index fossils are distinctive, widespread, and lived briefly. Their presence in a rock layer can be used to identify rocks that were deposited at that period of time over a large area. The fossil of a juvenile mammoth found near... | Radioactive isotopes can be used to estimate the ages of fossils and rocks. The method is called radioactive dating. Carbon-14 dating is an example of radioactive dating. It is illustrated in the video at this URL: MEDIA Click image to the left or use the URL below. URL: | Fossils are our best form of evidence about Earth history, including the history of life. Along with other geological evidence from rocks and structures, fossils even give us clues about past climates, the motions of plates, and other major geological events. Since the present is the key to the past, what we know about... |
Which series of landforms shows the correct order in which a stretch of rocky shoreline may be eroded? | Erosion by waves can create unique landforms (Figure 10.12). Wave-cut cliffs form when waves erode a rocky shoreline. They create a vertical wall of exposed rock layers. Sea arches form when waves erode both sides of a cliff. They create a hole in the cliff. Sea stacks form when waves erode the top of a sea arch. This ... | Runoff, streams, and rivers carry sediment to the oceans. The sediment in ocean water acts like sandpaper. Over time, they erode the shore. The bigger the waves are and the more sediment they carry, the more erosion they cause. | If you take away the water in the oceans (Figure 2.6), Earth looks really different. You see that the surface has two main features: continents and ocean basins. Continents are large land areas. Ocean basins extend from the edges of continents to the ocean floor and into deep trenches. Continents are much older than oc... | Rock layers extend laterally, or out to the sides. They may cover very broad areas, especially if they formed at the bottom of ancient seas. Erosion may have worn away some of the rock, but layers on either side of eroded areas will still match up. Look at the Grand Canyon in Figure 11.8. Its a good example of lateral ... | Sedimentary rocks follow certain rules. 1. Sedimentary rocks are formed with the oldest layers on the bottom and the youngest on top. 2. Sediments are deposited horizontally, so sedimentary rock layers are originally horizontal, as are some vol- canic rocks, such as ash falls. 3. Sedimentary rock layers that are not ho... | Geologists know about marine transgressions and regressions from the sedimentary rock record. These events leave characteristic rock layers known as sedimentary facies. On a shoreline, sand and other coarse grained rock fragments are commonly found on the beach where the wave energy is high. Away from the shore in lowe... |
if a measurement is precise, it must also be accurate. | The accuracy of a measurement is how close the measurement is to the true value. If you were to hit four different golf balls toward an over-sized hole, all of them might land in the hole. These shots would all be accurate because they all landed in the hole. This is illustrated in the sketch below. | As you can see from the sketch above, the four golf balls did not land as close to one another as they could have. Each one landed in a different part of the hole. Therefore, these shots are not very precise. The precision of measurements is how close they are to each other. If you make the same measurement twice, the ... | How can scientists know if a model designed to predict the future is likely to be accurate, since it may not be possible to wait long enough to see if the prediction comes true? One way is to run the model using a time in the past as the starting point see if the model can accurately predict the present. A model that c... | All chemical equations, like equations in math, must balance. This means that there must be the same number of each type of atom on both sides of the arrow. Thats because matter is always conserved in a chemical reaction. This is the law of conservation of mass. Look at the equation above for the reaction between carbo... | The girls in the picture above make up a small samplethere are only four of them. In scientific investigations, samples may include hundreds or even thousands of people or other objects of study. Especially when samples are very large, its important to be able to summarize their overall characteristics with a few numbe... | To get the correct answer in the volume calculation above, rounding was necessary. Rounding is done when one or more ending digits are dropped to get the correct number of significant figures. In this example, the answer was rounded down to a lower number (from 1.2 to 1). Sometimes the answer is rounded up to a higher ... |
which of the following causes asthma? | Asthma is a chronic illness in which the bronchioles, the tiny branches into which the bronchi are divided, become inflamed and narrow ( Figure 1.2). The muscles around the bronchioles contract, which narrows the airways. Large amounts of mucus are also made by the cells in the lungs. People with asthma have difficulty... | Different pollutants have different health effects: Lead is the most common toxic material and is responsible for lead poisoning. Carbon monoxide can kill people in poorly ventilated spaces, such as tunnels. Nitrogen and sulfur-oxides cause lung disease and increased rates of asthma, emphysema, and viral infections suc... | Many respiratory diseases are caused by pathogens. A pathogen is an organism that causes disease in another organism. Certain bacteria, viruses, and fungi are pathogens of the respiratory system. The common cold and flu are caused by viruses. The influenza virus that causes the flu is pictured below ( Figure 1.6). Tube... | The World Health Organization (WHO) reports that 2.4 million people die each year from causes directly related to air pollution. This includes both outdoor and indoor air pollution. Worldwide, there are more deaths linked to air pollution each year than to car accidents. Research by the WHO also shows that the worst ai... | Respiratory diseases are diseases of the lungs, bronchial tubes, trachea, nose, and throat ( Figure 1.1). These diseases can range from a mild cold to a severe case of pneumonia. Respiratory diseases are common. Many are easily treated, while others may cause severe illness or death. Some respiratory diseases are cause... | Many but not all cases of asthma can be linked to air pollution. During the 1996 Olympic Games, Atlanta, Georgia, closed off their downtown to private vehicles. This action decreased ozone levels by 28%. At the same time, there were 40% fewer hospital visits for asthma. Can scientists conclude without a shadow of a dou... |
a key bed must | Like index fossils, key beds are used to match rock layers. A key bed is a thin layer of rock. The rock must be unique and widespread. For example, a key bed from around the time that the dinosaurs went extinct is very important. A thin layer of clay was deposited over much of Earths surface. The clay has large amount ... | James Hutton came up with this idea in the late 1700s. The present is the key to the past. He called this the principle of uniformitarianism. It is that if we can understand a geological process now and we find evidence of that same Checkerboard Mesa in Zion National Park, Utah. process in the past, then we can assume ... | Enzymes increase the rate of chemical reactions by reducing the amount of activation energy needed for reactants to start reacting. One way this can happen is modeled in the Figure 1.1. Enzymes arent changed or used up in the reactions they catalyze, so they can be used to speed up the same reaction over and over again... | The genetic code has three other important characteristics. The genetic code is the same in all living things. This shows that all organisms are related by descent from a common ancestor. Each codon codes for just one amino acid (or start or stop). This is necessary so the correct amino acid is always selected. Most am... | Other levers change force or distance in different ways than a hammer removing a nail. How a lever changes force or distance depends on the location of the input and output forces relative to the fulcrum. The input force is the force applied by the user to the lever. The output force is the force applied by the lever t... | The nervous system is such an important part of your body. You want it to work at its best so that you can be at your best. Your nervous system contains what is probably the most important part of your body, which, of course, is your brain. Your brain allows you to learn. It allows you to feel emotions like love, anger... |
which of the following can lead to acne? | Conditions that irritate, clog or inflame your skin can cause symptoms such as redness, swelling, burning and itching. Allergies, irritants, your genetic background and certain diseases and immune system problems can cause numerous skin conditions. Many skin problems, such as acne, also affect your appearance. Acne You... | Forms of radiation that cause cancer include ultraviolet (UV) radiation and radon ( Figure 1.3). UV radiation is part of sunlight. It is the leading cause of skin cancer. Radon is a natural radioactive gas that seeps into buildings from the ground. It can cause lung cancer. | Other pathogens spread when they get on objects or surfaces. A fungus may spread in this way. For example, you can pick up the fungus that causes athletes foot by wearing shoes that an infected person has worn. You can also pick up this fungus from the floor of a public shower or other damp areas. After acne, athletes ... | Most cancers are caused by mutations. Mutations are random errors in genes. Mutations that lead to cancer usually occur in genes that control the cell cycle. Because of the mutations, abnormal cells are allowed to divide. Some mutations that lead to cancer may be inherited. However, most of the mutations are caused by ... | Some sunlight is good for your health. Vitamin D is made in the skin when it is exposed to sunlight. But getting too much sun can be unhealthy. A sunburn is a burn to the skin that is caused by overexposure to UV radiation from the suns rays or tanning beds. Light-skinned people, like the man pictured below ( Figure 1.... | Pathogens that cause cancer include the human papilloma virus (HPV) ( Figure 1.1) and the hepatitis B virus. HPV is spread through sexual contact. It can cause cancer of the reproductive system in females. The hepatitis B virus is spread through sexual contact or contact with blood containing the virus. It can cause ca... |
although the temperature of the mesosphere is extremely low, a persons blood would boil at normal body temperature. | The air in the mesosphere has extremely low density: 99.9% of the mass of the atmosphere is below the mesosphere. As a result, air pressure is very low (Figure 1.1). A person traveling through the mesosphere would experience severe burns from ultraviolet light since the ozone layer, which provides UV protection, is in ... | There are very few gas molecules in the mesosphere. This means that there is little matter to absorb the Suns rays and heat the air. Most of the heat that enters the mesosphere comes from the stratosphere below. Thats why the mesosphere is warmest at the bottom. | At the top of the mesosphere is the mesopause. Temperatures here are colder than anywhere else in the atmosphere. They are as low as -100 C (-212 F)! Nowhere on Earths surface is that cold. | The mesosphere is the layer above the stratosphere. It rises to about 85 kilometers (53 miles) above the surface. Temperature decreases with altitude in this layer. | The density of molecules is so low in the thermosphere that one gas molecule can go about 1 km before it collides with another molecule. Since so little energy is transferred, the air feels very cold (See opening image). | When you walk outside on a cool day, does your body temperature drop? No, your body temperature stays stable at around 98.6 degrees Fahrenheit. Even when the temperature around you changes, your internal temperature stays the same. This ability of the body to maintain a stable internal environment despite a changing en... |
how does mining affect streams and lakes? | Although mining provides people with many needed resources, the environmental costs can be high. Surface mining clears the landscape of trees and soil, and nearby streams and lakes are inundated with sediment. Pollutants from the mined rock, such as heavy metals, enter the sediment and water system. Acids flow from som... | Around the world, coal is the largest source of energy for electricity. The United States is rich in coal. Pennsylvania and the region to the west of the Appalachian Mountains are some of the most coal-rich areas of the United States. Coal has to be mined to get it out of the ground. Coal mining affects the environment... | For coal to be used as an energy source, it must first be mined. Coal mining occurs at the surface or underground by methods that are described in the the chapter Materials of Earths Crust (Figure 1.4). Mining, especially underground The location of the continents during the Carboniferous period. Notice that quite a lo... | Oil and natural gas lie below some regions of the seafloor. Large drills on floating oil rigs must be used to reach them. This is risky for workers on the rigs. It is also risky for the ocean and its living things. An oil rig explosion caused a massive oil leak in the Gulf of Mexico in 2010. Oil poured into the water f... | As a stream flows from higher elevations, like in the mountains, towards lower elevations, like the ocean, the work of the stream changes. At a streams headwaters, often high in the mountains, gradients are steep (Figure 1.3). The stream moves fast and does lots of work eroding the stream bed. Headwaters of the Roaring... | Fertilizers that run off of lawns and farm fields are extremely harmful to the environment. Nutrients, such as nitrates, in the fertilizer promote algae growth in the water they flow into. With the excess nutrients, lakes, rivers, and bays become clogged with algae and aquatic plants. Eventually these organisms die and... |
A neon light produces violet or blue light. | A neon light produces visible light by electroluminescence. In this process, neon or some other gas gives off light when an electric current passes through it. Other halogen gases besides neonincluding krypton and argonalso produce light in this way. The word OPEN in the sign 1.3 is a neon light. It is a long glass tub... | The classroom in Figure 22.1 has artificial light sources in addition to natural sunlight. There are fluorescent lights on the ceiling of the room. There are also projectors on the ceiling that are shining light on screens. In these and most other artificial light sources, electricity provides the energy and some type ... | Some objects produce light without becoming very hot. They generate light through chemical reactions or other processes. Producing light without heat is called luminescence. Luminescence, in turn, can occur in several different ways: One type of luminescence is called fluorescence. In this process, a substance absorbs ... | The human eye can distinguish only red, green, and blue light. These three colors are called the primary colors of light. All other colors of light can be created by combining the primary colors. Look at the Venn diagram 1.5. Red and green light combine to form yellow light. Red and blue light combine to form magenta l... | Visible light consists of a range of wavelengths. The wavelength of visible light determines the color that the light appears. As you can see in Figure 22.4, light with the longest wavelength appears red, and light with the shortest wavelength appears violet. In between is a continuum of all the other colors of light. ... | Have you ever seen a brilliant light show in the night sky? Sometimes the ions in the thermosphere glow at night. Storms on the Sun energize the ions and make them light up. In the Northern Hemisphere, the lights are called the northern lights, or aurora borealis. In the Southern Hemisphere, they are called southern li... |
_A total of four mass extinctions have occurred on Earth since life began. | At the end of the Precambrian, a mass extinction occurred. In a mass extinction, the majority of species die out. The Precambrian mass extinction was the first of six mass extinctions that occurred on Earth. Its not certain what caused this first mass extinction. Changes in Earths geology and climate were no doubt invo... | Its always fun to think about geologic time in a framework that we can more readily understand. Here are when some major events in Earth history would have occurred if all of earth history was condensed down to one calendar year. January 1 12 am: Earth forms from the planetary nebula - 4600 million years ago February 2... | Earth formed 4.5 billion years ago. Geologists divide this time span into smaller periods. Many of the divisions mark major events in life history. | Earths climate has changed many times through Earths history. Its been both hotter and colder than it is today. | Its hard to grasp the vast amounts of time since Earth formed and life first appeared. It may help to think of Earths history as a 24-hour day. | Astronomers have carried out computer simulations that are consistent with these facts and have detailed a birth story for the Moon. A little more than 4.5 billion years ago, roughly 70 million years after Earth formed, planetary bodies were being pummeled by asteroids and planetoids of all kinds. Earth was struck by a... |
the water in the ogallala aquifer is mostly from the last ice age. | The Ogallala Aquifer supplies about one-third of the irrigation water in the United States. The Ogallala Aquifer is widely used by people for municipal and agricultural needs. (Figure 1.2). The aquifer is found from 30 to 100 meters deep over an area of about 440,000 square kilometers! The water in the aquifer is mostl... | One of the biggest aquifers in the world is the Ogallala aquifer. As you can see from Figure 13.13, this aquifer lies beneath parts of eight U.S. states. It covers a total area of 451,000 square kilometers (174,000 square miles). In some places, it is less than a meter deep. In other places, it is hundreds of meters de... | Most of Earths water is stored in the oceans, where it can remain for hundreds or thousands of years. | Pangaea was the last supercontinent on Earth. Evidence for the existence of Pangaea was what Alfred Wegener used to create his continental drift hypothesis, which was described in the chapter Plate Tectonics. As the continents move and the land masses change shape, the shape of the oceans changes too. During the time o... | The oceans are an essential part of Earths water cycle. Since they cover so much of the planet, most evaporation comes from oceans and most precipitation falls on oceans. | In regions where summers are long and dry, melting glaciers in mountain regions provide an important source of water for organisms and often for nearby human populations. Click image to the left or use the URL below. URL: |
primary component of photochemical smog | Photochemical smog, a different type of air pollution, first became a problem in Southern California after World War II. The abundance of cars and sunshine provided the perfect setting for a chemical reaction between some of the molecules in auto exhaust or oil refinery emissions and sunshine (Figure 1.2). Photochemica... | Another example of a synthesis reaction is illustrated in Figure 8.7. The brown haze in the air over the city of Los Angeles is smog. A major component of smog is nitrogen dioxide (NO2 ). It forms when nitric oxide (NO), from sources such as car exhaust, combines with oxygen (O2 ) in the air. The equation for this reac... | Some primary pollutants are natural, such as volcanic ash. Dust is natural but exacerbated by human activities; for example, when the ground is torn up for agriculture or development. Most primary pollutants are the result of human activities, the direct emissions from vehicles and smokestacks. Primary pollutants inclu... | What goes into the plant cell to start photosynthesis? The reactants of photosynthesis are carbon dioxide and water. These are the molecules necessary to begin the process. But one more item is necessary, and that is sunlight. All three components, carbon dioxide, water, and the suns energy are necessary for photosynth... | The overall chemical reaction for photosynthesis is 6 molecules of carbon dioxide (CO2 ) and 6 molecules of water (H2 O), with the addition of solar energy. This produces 1 molecule of glucose (C6 H12 O6 ) and 6 molecules of oxygen Stomata are special pores that allow gasses to enter and exit the leaf. (O2 ). Using che... | Primary pollutants enter the air directly. Some are released by natural processes, like ash from volcanoes. Most are released by human activities. They pour into the air from vehicles and smokestacks. Several of these pollutants are described below. Carbon oxides include carbon monoxide (CO) and carbon dioxide (CO2 ). ... |
Mechanical digestion takes place in the | As food is pushed through the GI tract by peristalsis, it undergoes digestion. Digestion is the process of breaking down food into nutrients. There are two types of digestion: mechanical digestion and chemical digestion. Mechanical digestion occurs when large chunks of food are broken down into smaller pieces. This is ... | The mouth is the first organ that food enters. But digestion may start even before you put the first bite of food into your mouth. Just seeing or smelling food can cause the release of saliva and digestive enzymes in your mouth. This diagram shows how muscles push food through the digestive system. Muscle contractions ... | The mouth and stomach are just two of the organs of the digestive system. Other digestive system organs are the esophagus, small intestine, and large intestine. Below, you can see that the digestive organs form a long tube ( Figure 1.1). In adults, this tube is about 30 feet long! At one end of the tube is the mouth. A... | Chemical digestion could not take place without the help of digestive enzymes and other substances secreted into the GI tract. An enzyme is a protein that speeds up a biochemical reaction. Digestive enzymes speed up the reactions of chemical digestion. Table 17.3 lists a few digestive enzymes, the organs that produce t... | Nutrients in the foods you eat are needed by the cells of your body. How do the nutrients in foods get to your body cells? What organs and processes break down the foods and make the nutrients available to cells? The organs are those of the digestive system. The processes are digestion and absorption. The digestive sys... | The digestive system is the body system that breaks down food and absorbs nutrients. It also eliminates solid food wastes that remain after food is digested. The major organs of the digestive system are shown in Figure 17.10. For an entertaining overview of the digestive system and how it works, watch this video: MEDI... |
The space shuttle program flew a total of 10 missions. | The space shuttle program has been very successful. Over 100 mission have been flown. Space shuttle missions have made many scientific discoveries. Crews have launched many satellites. There have been other great achievements in space. However, the program has also had two tragic disasters. The first came just 73 secon... | NASA wanted a new kind of space vehicle. This vehicle had to be reusable. It had to able to carry large pieces of equipment, such as satellites, space telescopes, or sections of a space station. The new vehicle was called a space shuttle, shown in Figure 23.25. There have been five space shuttles: Columbia, Challenger,... | The International Space Station, shown in Figure 23.24 is a joint project between the space agencies of many nations These include the United States (NASA), Russia (RKA), Japan (JAXA), Canada (CSA), several European countries (ESA) and the Brazilian Space Agency. The International Space Station is a very large station.... | Between 1971 and 1982, the Soviets put a total of seven Salyut space stations into orbit. Figure 23.22 shows the last of these, Salyut 7. These were all temporary stations. They were launched and later inhabited by a human crew. Three of the Salyut stations were used for secret military purposes. The others were used t... | In response to Sputnik program, the U.S. launched two satellites. Explorer I was launched on January 31, 1958 and Vanguard 1 on March 17, 1958. National Aeronautics and Space Administration (NASA) was established that same year. The race was on! On April 12, 1961, a Soviet cosmonaut became the first human in space and ... | Incredible images have come from the Hubble Space Telescope (HST). Even more incredible scientific discoveries have come from HST. The Hubble was the first telescope in space. It was put into orbit by the space shuttle Discovery in 1990. Since then, four shuttle missions have gone to the Hubble to make repairs and upgr... |
Which of the following equations represents alpha decay? | Alpha decay occurs when an unstable nucleus emits an alpha particle and energy. The diagram in Figure 11.6 represents alpha decay. An alpha particle contains two protons and two neutrons, giving it a charge of +2. A helium nucleus has two protons and two neutrons, so an alpha particle is represented in nuclear equation... | There are several types of radioactive decay, including alpha, beta, and gamma decay. In all three types, nuclei emit radiation, but the nature of the radiation differs. The Table 1.1 shows the radiation emitted in each type of decay. Type Alpha decay Beta decay Gamma decay Radiation Emitted alpha particle (2 protons a... | Both alpha and beta decay change the number of protons in an atoms nucleus, thereby changing the atom to a different element. In alpha decay, the nucleus loses two protons. In beta decay, the nucleus either loses a proton or gains a proton. In gamma decay, no change in proton number occurs, so the atom does not become ... | In alpha and beta decay, both particles and energy are emitted. In gamma decay, only energy is emitted. Gamma decay occurs when an unstable nucleus gives off gamma rays. Gamma rays, like rays of visible light and X-rays, are waves of energy that travel through space at the speed of light. Gamma rays have the greatest a... | There are three types of radioactive decay: alpha, beta, and gamma decay. In all three types, nuclei emit radiation, but the nature of that radiation differs from one type of decay to another. You can watch a video about the three types at this URL: (17:02). MEDIA Click image to the left or use the URL below. URL: | Beta decay occurs when an unstable nucleus emits a beta particle and energy. A beta particle is an electron. It has a charge of -1. In nuclear equations, a beta particle is represented by the symbol 01 e. The subscript -1 represents the particles charge, and the superscript 0 shows that the particle has virtually no ma... |
Which of the following is a problem in using nuclear fusion for energy? | Scientists are searching for ways to create controlled nuclear fusion reactions on Earth. Their goal is develop nuclear fusion power plants, where the energy from fusion of hydrogen nuclei can be converted to electricity. How this might work is shown in Figure 11.17. The use of nuclear fusion for energy has several pro... | Nuclear fusion is the opposite of nuclear fission. In fusion, two or more small nuclei combine to form a single, larger nucleus. An example is shown in Figure 11.15. In this example, two hydrogen nuclei fuse to form a helium nucleus. A neutron and a great deal of energy are also released. In fact, fusion releases even ... | In the U.S., the majority of electricity is produced by burning coal or other fossil fuels. This causes air pollution that harms the health of living things. The air pollution also causes acid rain and contributes to global warming. In addition, fossil fuels are nonrenewable resources, so if we keep using them, they wi... | Nuclear power is clean. It does not pollute the air. However, the use of nuclear energy does create other environ- mental problems. Uranium must be mined (Figure 1.3). The process of splitting atoms creates radioactive waste, which remains dangerous for thousands or hundreds of thousands of years. As yet, there is no l... | Like fossil fuels, the radioactive element uranium can be used to generate electrical energy in power plants. This source of energy is known as nuclear energy. In a nuclear power plant, the nuclei of uranium atoms are split apart into smaller nuclei in the process of nuclear fission. This process releases a tremendous ... | Like fossil fuels, the radioactive element uranium can be used to generate electrical energy in power plants. In a nuclear power plant, the nuclei of uranium atoms are split in the process of nuclear fission. This process releases a tremendous amount of energy from just a small amount of uranium. The total supply of ur... |
A metallic bond may form between a metal and any other element. | Metallic bonds are forces of attraction between positive metal ions and the valence electrons that are constantly moving around them (see the Figure 1.1). The valence electrons include their own and those of other, nearby ions of the same metal. The valence electrons of metals move freely in this way because metals hav... | Not all chemical bonds form in the same way as the bonds in water. There are actually three different types of chemical bonds, called covalent, ionic, and metallic bonds. Each type of bond is described below. Click image to the left or use the URL below. URL: A covalent bond is the force of attraction that holds toget... | An alloy is a mixture of a metal with one or more other elements. The other elements may be metals, nonmetals, or both. An alloy is formed by melting a metal and dissolving the other elements in it. The molten solution is then allowed to cool and harden. Alloys generally have more useful properties than pure metals. Se... | Ionic bonds form only between metals and nonmetals. Thats because metals want to give up electrons, and nonmetals want to gain electrons. Find sodium (Na) in the Figure 1.2. Sodium is an alkali metal in group 1. Like all group 1 elements, it has just one valence electron. If sodium loses that one electron, it will have... | A chemical bond is a force of attraction between atoms or ions. Bonds form when atoms share or transfer valence electrons. Valence electrons are the electrons in the outer energy level of an atom that may be involved in chemical interactions. Valence electrons are the basis of all chemical bonds. Q: Why do you think th... | Because of their freely moving electrons, metals are good conductors of electricity. Metals also can be shaped without breaking. They are ductile (can be shaped into wires) and malleable (can be shaped into thin sheets). Metals have these properties because of the nature of their metallic bonds. A metallic lattice, lik... |
which of these help to verify the composition of earths core? | At the planets center lies a dense metallic core. Scientists know that the core is metal because: 1. The density of Earths surface layers is much less than the overall density of the planet, as calculated from the planets rotation. If the surface layers are less dense than average, then the interior must be denser than... | Earth formed like the other planets. Different materials in its region of space collided. Eventually the material made a planet. All of the collisions caused Earth to heat up. Rock and metal melted. The molten material separated into layers. Gravity pulled the denser material into the center. The lighter elements rose ... | When Earth was entirely molten, gravity drew denser elements to the center and lighter elements rose to the surface. The separation of Earth into layers based on density is known as differentiation. The densest material moved to the center to create the planets dense metallic core. Materials that are intermediate in de... | The idea that Earth is a magnet is far from new. It was first proposed in 1600 by a British physician named William Gilbert. However, explaining why Earth acts like a magnet is a relatively recent discovery. It had to wait until the development of technologies such as seismographs, which detect and measure earthquake w... | As you walk, the ground usually looks pretty flat, even though the Earth is round. How do we know this? We have pictures of Earth taken from space that show that Earth is round. Astronauts aboard the Apollo 17 shuttle took this one, called The Blue Marble (Figure 24.1). Earth looks like a giant blue and white ball. Lon... | Earth is surrounded by a magnetic field (Figure 1.1) that behaves as if the planet had a gigantic bar magnet inside of it. Earths magnetic field also has a north and south pole. The magnetic field arises from the convection of molten iron and nickel metals in Earths liquid outer core. |
homogeneous mixture in which particles are big enough to reflect light | Mixtures have different properties depending on the size of their particles. Three types of mixtures based on particle size are described below. Figure 3.13 shows examples of each type. You can watch videos about the three types of mixtures at these links: MEDIA Click image to the left or use the URL below. URL: MEDIA... | Many objects have color because they contain pigments. A pigment is a substance that colors materials by reflecting light of certain wavelengths and absorbing light of other wavelengths. A very common pigment is chlorophyll, which is found in plants. This dark green pigment absorbs all but green wavelengths of visible ... | Some mixtures are homogeneous. This means they have the same composition throughout. An example is salt water in the ocean. Ocean water everywhere is about 3.5 percent salt. Some mixtures are heterogeneous. This means they vary in their composition. An example is trail mix. No two samples of trail mix, even from the sa... | Compounds that form from two or more nonmetallic elements, such as carbon and hydrogen, are called covalent compounds. In a covalent compound, atoms of the different elements are held together in molecules by covalent bonds. These are chemical bonds in which atoms share valence electrons. The force of attraction betwee... | When you look at the sky on a clear night, you can see dozens, perhaps even hundreds, of tiny points of light. Almost every one of these points of light is a star, a giant ball of glowing gas at a very, very high temperature. Stars differ in size, temperature, and age, but they all appear to be made up of the same elem... | A compound is a unique substance that forms when two or more elements combine chemically. For example, the compound carbon dioxide forms when one atom of carbon (grey in the model above) combines with two atoms of oxygen (red in the model). Another example of a compound is water. It forms when two hydrogen atoms combin... |
The resting position of a transverse wave is called a trough. | A transverse wave is characterized by the high and low points reached by particles of the medium as the wave passes through. The high points are called crests, and the low points are called troughs. You can see both in the Figure below. | A transverse wave is a wave in which particles of the medium vibrate at right angles, or perpendicular, to the direction that the wave travels. Another example of a transverse wave is the wave that passes through a rope with you shake one end of the rope up and down, as in the Figure 1.1. The direction of the wave is d... | When a wave is reflected straight back from an obstacle, the reflected wave interferes with the original wave and creates a standing wave. This is a wave that appears to be standing still. A standing wave occurs because of a combination of constructive and destructive interference between a wave and its reflected wave.... | Energy is transmitted in waves. Every wave has a high point called a crest and a low point called a trough. The height of a wave from the center line to its crest is its amplitude. The distance between waves from crest to crest (or trough to trough) is its wavelength. The parts of a wave are illustrated in Figure 1.1. | Another example of transverse waves occurs with earthquakes. The disturbance that causes an earthquake sends transverse waves through underground rocks in all directions from the disturbance. Earthquake waves that travel this way are called secondary, or S, waves. An S wave is illustrated in Figure 19.4. | Transverse waves called S waves occur during earthquakes. The disturbance that causes an earthquake sends transverse waves through underground rocks in all directions away from the disturbance. S waves may travel for hundreds of miles. An S wave is modeled in the Figure 1.3. |
Normal rain is slightly acidic because it contains dissolved | Acid rain is rain that has a pH less than 5 (see Figure 22.9). The pH of normal rain is 5.6. Its slightly acidic because carbon dioxide in the air dissolves in rain. This forms carbonic acid, a weak acid. | Acid rain forms when nitrogen and sulfur oxides in air dissolve in rain (see Figure 22.10). This forms nitric and sulfuric acids. Both are strong acids. Acid rain with a pH as low as 4.0 is now common in many areas. Acid fog may be even more acidic than acid rain. Fog with a pH as low as 1.7 has been recorded. Thats th... | Acid rain water is more acidic than normal rain water. Acidity is measured on the pH scale. Lower numbers are more acidic and higher numbers are less acidic (also called more alkaline) (Figure 1.3). Natural rain is somewhat acidic, with a pH of 5.6; acid rain must have a pH of less than 5.0. A small change in pH repres... | Acid rain is caused by sulfur and nitrogen oxides emanating from power plants or metal refineries. The smokestacks have been built tall so that pollutants dont sit over cities (Figure 1.1). As they move, these pollutants combine with water vapor to form sulfuric and nitric acids. The acid droplets form acid fog, rain, ... | Air pollution may also cause acid rain. This is rain that is more acidic (has a lower pH) than normal rain. Acids form in the atmosphere when nitrogen and sulfur oxides mix with water in air. Nitrogen and sulfur oxides come mainly from motor vehicle exhaust and coal burning. If acid rain falls into lakes, it lowers the... | One result of air pollution is acid rain. Acid rain is precipitation with a low (acidic) pH. This rain can be very destructive to wildlife. When acid rain falls in forests, freshwater habitats, or soils, it can kill insects and aquatic life. It causes this damage because of its very low pH. Sulfur oxides and nitrogen o... |
Temperature is a physical property of matter. | No doubt you already have a good idea of what temperature is. You might define it as how hot or cold something feels. In physics, temperature is defined as the average kinetic energy of the particles in an object. When particles move more quickly, temperature is higher and an object feels warmer. When particles move mo... | The atoms that make up matter are in constant motion, so they have kinetic energy. All that motion gives matter thermal energy. Thermal energy is defined as the total kinetic energy of all the atoms that make up an object. It depends on how fast the atoms are moving and how many atoms the object has. Therefore, an obje... | If two objects have the same mass, the object with the higher temperature has greater thermal energy. Temperature affects thermal energy, but temperature isnt the same thing as thermal energy. Thats because an objects mass also affects its thermal energy. The examples in Figure 18.1 make this clear. In the figure, the ... | Temperature is measured with a thermometer. A thermometer shows how hot or cold something is relative to two reference temperatures, usually the freezing and boiling points of water. Scientists often use the Celsius scale for temperature. On this scale, the freezing point of water is 0C and the boiling point is 100C. T... | Thermal energy and temperature are closely related. Both reflect the kinetic energy of moving particles of matter. However, temperature is the average kinetic energy of particles of matter, whereas thermal energy is the total kinetic energy of particles of matter. Does this mean that matter with a lower temperature has... | Convection is the transfer of thermal energy by particles moving through a fluid (either a gas or a liquid). Thermal energy is the total kinetic energy of moving particles of matter, and the transfer of thermal energy is called heat. Convection is one of three ways that thermal energy can be transferred (the other ways... |
When a kangaroo jumps, the kangaroos action force acts on the ground and the reaction force | Newtons third law of motion states that every action has an equal and opposite reaction. This means that forces always act in pairs. First an action occurs, such as the skateboarders pushing together. Then a reaction occurs that is equal in strength to the action but in the opposite direction. In the case of the skateb... | Newtons third law of motion explains how Jerod starts his skateboard moving. This law states that every action has an equal and opposite reaction. This means that forces always act in pairs. First an action occursJerod pushes against the ground with his foot. Then a reaction occursJerod moves forward on his skateboard.... | Because action and reaction forces are equal and opposite, you might think they would cancel out, as balanced forces do. But you would be wrong. Balanced forces are equal and opposite forces that act on the same object. Thats why they cancel out. Action-reaction forces are equal and opposite forces that act on differen... | The forces involved in actions and reactions can be represented with arrows. The way an arrow points shows the direction of the force, and the size of the arrow represents the strength of the force. Look at the skateboarders in the Figure 1.1. In the top row, the arrows represent the forces with which the skateboarders... | Whenever an object speeds up, slows down, or changes direction, it accelerates. Acceleration occurs whenever an unbalanced force acts on an object. Two factors affect the acceleration of an object: the net force acting on the object and the objects mass. Newtons second law of motion describes how force and mass affect ... | What do all the photos in Figure 17.3 have in common? All of them show things that are moving. Kinetic energy is the energy of moving matter. Anything that is moving has kinetic energy from the atoms in matter to the planets in solar systems. Things with kinetic energy can do work. For example, the hammer in the photo ... |
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